This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A212805 #13 Dec 30 2023 13:48:26
%S A212805 2,1,3,162,269568,21772800000,128430157824000000,
%T A212805 78734235726376796160000000,6793969131008738346811156070400000000,
%U A212805 107405833909078014660339510303458240495616000000000,392460917103771065568880570648836410770980864000000000000000000000,407931390497527236736237611020825246476822200409679741237329920000000000000000000000
%N A212805 a(n) = (1-(n-1)/2^n)*(n!)^n.
%H A212805 Morton Abramson, David Promislow, <a href="https://doi.org/10.1016/0097-3165(78)90012-2">Enumeration of arrays by column rises</a>, J. Combinatorial Theory Ser. A 24 (1978), no. 2, 247--250. MR0469773 (57 #9554).
%t A212805 Table[(1-(n-1)/2^n)(n!)^n,{n,0,15}] (* _Harvey P. Dale_, Dec 30 2023 *)
%o A212805 (PARI) a(n) = (1-(n-1)/2^n)*(n!)^n; \\ _Michel Marcus_, Feb 27 2018
%Y A212805 Cf. A212806.
%K A212805 nonn
%O A212805 0,1
%A A212805 _N. J. A. Sloane_, May 27 2012